The present invention relates to a semiconductor cooling apparatus in which flexible cooling passageways are brought into contact with heated members of electronic components such as semiconductor elements, and cooling water is caused to flow through the cooling passageways, thereby cooling the heated members.
In a conventional apparatus, as shown in, for example, Japanese Patent Unexamined Publication Nos. 59-200495, 61-32449, and 60-160150 and U.S. Pat. No. 3,703,668, cooling fins are mounted on a back surface of a heated element (for example, a semiconductor chip) and water is caused to flow through the cooling fins to cool the heated member. It is common to mount a plurality of heating chips on a base plate, and to connect wires of the chips to wirings of the base plate according to a flip chip method (soldering balls) so that signals are applied through such wiring arrangement. On the other hand, on the back surface of the heated chip, there are provided inlet and outlet cooling water passageways that are formed of flexible material. The flexible structure is metallically coupled with a cooling water header through an O-ring or soldering. In some cases, two separate cooling water passages one for an inlet and one for an outlet, are provided in a single chip, and in other cases, a double or coaxial passage is provided for the single chip. In any case, such a flexible structure serves to prevent stress due to a shift of the cooling water header from directly affecting the chip as much as possible. The heated chip is cooled through cooling fins by the cooling water flowing through the flexible assembly. The cooling fins and the heating member are metallically coupled with each other or are coupled with each other through high heat conductive material such as silicone oil and grease. In any case, means for enhancing the heat conductivity is provided at this portion.
A semiconductor cooling structure to which the present invention pertains must be used for effectively cooling the heated chips and at the same time to suppress the stress applied to the heated chips as much as possible. Furthermore, since the heating chips are generally small in size (for example, 10 to 20 mm long) and are also arranged in high density, the cooling structure must be assembled or repaired in a limited space. Namely, the structure must have good assembling and repairing characteristics. Moreover, since the coolant is caused to flow through the narrow space, the pressure loss caused by the fluid resistance is likely to be large.
For example, according to one method, two flexible bellows are provided to the cooling structure, and are used as the inlet and outlet for the coolant. In this method, the flexible bellows and cooling blocks for covering the cooling fins on the chip back surface are coupled with each other by soldering, and also the cooling block and the heated chips are coupled with each other by soldering or the like. These flexible bellows are also connected to the cooling block provided on the back surfaces of the adjacent heating chips. It is therefore necessary to disassemble the cooling structure and to remove the heated chips in the case where there is a damaged heating chip even with the soldered cooling structure. In this case, if the respective components are coupled with each other by soldering or the like, the workability is very poor. On the other hand, it has been proposed to connect the flexible bellows and the cooling header, constituting the cooling structure, to each other by using O-rings to thereby enhance the assembling and repairing characteristics. However, in this case, the header of the coolant must be increased and a number of flexible bellows must be interposed between the base plate and the coolant header. It is therefore necessary to mount a number of flexible bellows through the O-rings onto the coolant header upon the assembling work. The cooling block provided at one end of the flexible bellows mounted at the other end to the cooling header is to be mounted on the heated chip. In this case, since it is impossible to connect the cooling block and the heated chip to each other by soldering or the like because of the narrowed space therebetween, it is necessary to, for example, assemble the cooling structure while clamping the heat conductive grease or heat conductive sheet between the cooling block and the heated chip. In this case, when it is necessary to remove the cooling structure due to damage to heated chip, it is possible to separate the structure at the heat conductive grease or heat conductive sheet. However, the cooling method in which the heat conductive grease or the heat conductive sheet is interposed between the cooling block and the heated chip is subjected to a large heat resistance in comparison with a method in which the cooling block and the heated chip are coupled directly to each other by soldering or the like. The indirect coupling method does not meet the requirement of the semiconductor cooling structure where the heating chips must be effectively cooled. Furthermore, due to the flow of the coolant in series in the cooling surfaces of the cooling blocks corresponding to the plurality of heated chips, the flow resistance will be increased in the cooling blocks to increase the pressure loss.